package src;

/**
 * 基于链表实现的字典
 */
public class LinkedMap<K, V> implements Map<K, V> {

    private class Node{
        public K key;
        public V value;
        public Node next;
        public Node(K key, V value, Node next){
            this.key = key;
            this.value = value;
            this.next = next;
        }
        public Node(){
            this(null, null, null);
        }

        @Override
        public String toString() {
            return key.toString() + ": " + value.toString();
        }
    }

    private Node dummyHead;
    private int size;
    public LinkedMap(){
        dummyHead = new Node();
        size = 0;
    }


    @Override
    public void add(K key, V value) {
        Node node = getNode(key);
        if (node == null) {
            dummyHead.next = new Node(key, value, dummyHead.next);
            size ++;
        }else{
            node.value = value;
        }
    }

    @Override
    public V remove(K key) {
        Node prev = dummyHead;
        while(prev.next != null){
            if (prev.next.key.equals(key)) {
                break;
            }
            prev = prev.next;
        }
        if (prev.next != null) {
            Node delNode = prev.next;
            prev.next = delNode.next;
            delNode.next = null;
            size --;
            return delNode.value;
        }else{
            return null;
        }

    }

    @Override
    public boolean contains(K key) {
        return getNode(key) != null;
    }

    @Override
    public V get(K key) {
        Node node = getNode(key);
        return node == null ? null: node.value;
    }

    @Override
    public void set(K key, V newValue) {
        Node node = getNode(key);
        if (node == null) {
            throw new IllegalArgumentException(key + " doesn't exist!");
        }
        node.value = newValue;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    private Node getNode(K key){
        Node cur = dummyHead.next;
        while(cur != null){
            if(cur.key.equals(key)){
                return cur;
            }
            cur = cur.next;
        }
        return null;
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        Node cur = dummyHead.next;
        int count = 1000;
        res.append("LinkedMap [");
        while(cur != null){
            if (count != 1000) res.append(", ");
            res.append(cur);
            cur = cur.next;
            if (count <= 0) {
                break;
            }
            count --;
        }
        res.append("]");
        return res.toString();
    }
}